This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-046270, filed Feb. 23, 2000; and No. 2000-046271, filed Feb. 23, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a connection structure and method for connecting a printed circuit such as a flexible printed circuit (hereinafter referred to as an xe2x80x9cFPCxe2x80x9d), and a metal terminal, and also to a reinforcing structure and method for reinforcing a junction between the printed circuit and the metal terminal.
In recent years, the number of electronic components used in vehicles has increased, and hence the influence of the increase in the weight of the wire harnesses in a vehicle upon the fuel consumption is becoming serious. Therefore, to reduce the weight of the wire harness, at least part of the wire harness has come to be replaced with an FPC harness. To connect an FPC to electrical wires, in general, terminal attachments secured to the tips of the electrical wires are connected with pressure to the FPC by means of an FPC connector (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-12328). Alternatively, piercing and soldering, etc. are used as other connection methods.
However, the method for simply connecting an FPC to terminal attachments by a connector with pressure cannot be employed in a circuit other than a low-current circuit. This is because, in the connection method, the pressure applied is low and the contact area of the FPC and the terminal attachments is small, and hence the contact resistance is inevitably high. When, for example, incorporating an FPC in a vehicle harness, there may be a case where the FPC is used as a high-current circuit of 10A or more. In this case, the FPC cannot be connected with a sufficiently low enough contact resistance to enable it to be used. Furthermore, a resin, the material of the base film of the FPC, deforms due to heat, which reduces the connection pressure over time and hence reduces the reliability of the circuit. In addition, piercing is not so reliable a method and accordingly cannot be used for a high-current circuit. In a method using solder, PET (polyethylene terephthalate) is often used as the base film of the FPC for reducing the cost. In this case, automatic soldering such as flow soldering cannot be executed in light of its heat resistance. Accordingly, the connection of the FPC to terminal attachments raises the unit price, in mass production terms.
It is an object of the invention to provide a connection method and structure for connecting a printed circuit to metal terminals, which enables a highly reliable, high-current-bearable connection of low contact resistance.
It is another object of the invention to provide a reinforcing method and structure suitable for junctions between a printed circuit, in particular, an FPC, and metal terminals.
The invention provides a method of connecting a printed circuit having wiring formed on a printed circuit board, to a metal terminal, wherein the wiring is directly connected to the metal terminal by one of resistance welding, ultrasonic welding and laser welding.
In the invention, an excellent electrical and mechanical connection can be realized between the printed circuit board and the metal terminal by directly connecting them, using one of resistance welding, ultrasonic welding and laser welding, or by forming a low-fusion-point metal layer on at least one of their to-be-connected surfaces, and melting the low-fusion-point metal layer to connect them.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.